3 menu "printk and dmesg options"
6 bool "Show timing information on printks"
9 Selecting this option causes time stamps of the printk()
10 messages to be added to the output of the syslog() system
11 call and at the console.
13 The timestamp is always recorded internally, and exported
14 to /dev/kmsg. This flag just specifies if the timestamp should
15 be included, not that the timestamp is recorded.
17 The behavior is also controlled by the kernel command line
18 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
20 config CONSOLE_LOGLEVEL_DEFAULT
21 int "Default console loglevel (1-15)"
25 Default loglevel to determine what will be printed on the console.
27 Setting a default here is equivalent to passing in loglevel=<x> in
28 the kernel bootargs. loglevel=<x> continues to override whatever
29 value is specified here as well.
31 Note: This does not affect the log level of un-prefixed printk()
32 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
35 config CONSOLE_LOGLEVEL_QUIET
36 int "quiet console loglevel (1-15)"
40 loglevel to use when "quiet" is passed on the kernel commandline.
42 When "quiet" is passed on the kernel commandline this loglevel
43 will be used as the loglevel. IOW passing "quiet" will be the
44 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
46 config MESSAGE_LOGLEVEL_DEFAULT
47 int "Default message log level (1-7)"
51 Default log level for printk statements with no specified priority.
53 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
54 that are auditing their logs closely may want to set it to a lower
57 Note: This does not affect what message level gets printed on the console
58 by default. To change that, use loglevel=<x> in the kernel bootargs,
59 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
61 config BOOT_PRINTK_DELAY
62 bool "Delay each boot printk message by N milliseconds"
63 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
65 This build option allows you to read kernel boot messages
66 by inserting a short delay after each one. The delay is
67 specified in milliseconds on the kernel command line,
70 It is likely that you would also need to use "lpj=M" to preset
71 the "loops per jiffie" value.
72 See a previous boot log for the "lpj" value to use for your
73 system, and then set "lpj=M" before setting "boot_delay=N".
74 NOTE: Using this option may adversely affect SMP systems.
75 I.e., processors other than the first one may not boot up.
76 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
77 what it believes to be lockup conditions.
80 bool "Enable dynamic printk() support"
86 Compiles debug level messages into the kernel, which would not
87 otherwise be available at runtime. These messages can then be
88 enabled/disabled based on various levels of scope - per source file,
89 function, module, format string, and line number. This mechanism
90 implicitly compiles in all pr_debug() and dev_dbg() calls, which
91 enlarges the kernel text size by about 2%.
93 If a source file is compiled with DEBUG flag set, any
94 pr_debug() calls in it are enabled by default, but can be
95 disabled at runtime as below. Note that DEBUG flag is
96 turned on by many CONFIG_*DEBUG* options.
100 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
101 which is contained in the 'debugfs' filesystem. Thus, the debugfs
102 filesystem must first be mounted before making use of this feature.
103 We refer the control file as: <debugfs>/dynamic_debug/control. This
104 file contains a list of the debug statements that can be enabled. The
105 format for each line of the file is:
107 filename:lineno [module]function flags format
109 filename : source file of the debug statement
110 lineno : line number of the debug statement
111 module : module that contains the debug statement
112 function : function that contains the debug statement
113 flags : '=p' means the line is turned 'on' for printing
114 format : the format used for the debug statement
118 nullarbor:~ # cat <debugfs>/dynamic_debug/control
119 # filename:lineno [module]function flags format
120 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
121 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
122 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
126 // enable the message at line 1603 of file svcsock.c
127 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
128 <debugfs>/dynamic_debug/control
130 // enable all the messages in file svcsock.c
131 nullarbor:~ # echo -n 'file svcsock.c +p' >
132 <debugfs>/dynamic_debug/control
134 // enable all the messages in the NFS server module
135 nullarbor:~ # echo -n 'module nfsd +p' >
136 <debugfs>/dynamic_debug/control
138 // enable all 12 messages in the function svc_process()
139 nullarbor:~ # echo -n 'func svc_process +p' >
140 <debugfs>/dynamic_debug/control
142 // disable all 12 messages in the function svc_process()
143 nullarbor:~ # echo -n 'func svc_process -p' >
144 <debugfs>/dynamic_debug/control
146 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
149 endmenu # "printk and dmesg options"
151 menu "Compile-time checks and compiler options"
154 bool "Compile the kernel with debug info"
155 depends on DEBUG_KERNEL && !COMPILE_TEST
157 If you say Y here the resulting kernel image will include
158 debugging info resulting in a larger kernel image.
159 This adds debug symbols to the kernel and modules (gcc -g), and
160 is needed if you intend to use kernel crashdump or binary object
161 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
162 Say Y here only if you plan to debug the kernel.
166 config DEBUG_INFO_REDUCED
167 bool "Reduce debugging information"
168 depends on DEBUG_INFO
170 If you say Y here gcc is instructed to generate less debugging
171 information for structure types. This means that tools that
172 need full debugging information (like kgdb or systemtap) won't
173 be happy. But if you merely need debugging information to
174 resolve line numbers there is no loss. Advantage is that
175 build directory object sizes shrink dramatically over a full
176 DEBUG_INFO build and compile times are reduced too.
177 Only works with newer gcc versions.
179 config DEBUG_INFO_SPLIT
180 bool "Produce split debuginfo in .dwo files"
181 depends on DEBUG_INFO
183 Generate debug info into separate .dwo files. This significantly
184 reduces the build directory size for builds with DEBUG_INFO,
185 because it stores the information only once on disk in .dwo
186 files instead of multiple times in object files and executables.
187 In addition the debug information is also compressed.
189 Requires recent gcc (4.7+) and recent gdb/binutils.
190 Any tool that packages or reads debug information would need
191 to know about the .dwo files and include them.
192 Incompatible with older versions of ccache.
194 config DEBUG_INFO_DWARF4
195 bool "Generate dwarf4 debuginfo"
196 depends on DEBUG_INFO
198 Generate dwarf4 debug info. This requires recent versions
199 of gcc and gdb. It makes the debug information larger.
200 But it significantly improves the success of resolving
201 variables in gdb on optimized code.
204 bool "Provide GDB scripts for kernel debugging"
205 depends on DEBUG_INFO
207 This creates the required links to GDB helper scripts in the
208 build directory. If you load vmlinux into gdb, the helper
209 scripts will be automatically imported by gdb as well, and
210 additional functions are available to analyze a Linux kernel
211 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
214 config ENABLE_MUST_CHECK
215 bool "Enable __must_check logic"
218 Enable the __must_check logic in the kernel build. Disable this to
219 suppress the "warning: ignoring return value of 'foo', declared with
220 attribute warn_unused_result" messages.
223 int "Warn for stack frames larger than (needs gcc 4.4)"
225 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
226 default 1280 if (!64BIT && PARISC)
227 default 1024 if (!64BIT && !PARISC)
228 default 2048 if 64BIT
230 Tell gcc to warn at build time for stack frames larger than this.
231 Setting this too low will cause a lot of warnings.
232 Setting it to 0 disables the warning.
235 config STRIP_ASM_SYMS
236 bool "Strip assembler-generated symbols during link"
239 Strip internal assembler-generated symbols during a link (symbols
240 that look like '.Lxxx') so they don't pollute the output of
241 get_wchan() and suchlike.
244 bool "Generate readable assembler code"
245 depends on DEBUG_KERNEL
247 Disable some compiler optimizations that tend to generate human unreadable
248 assembler output. This may make the kernel slightly slower, but it helps
249 to keep kernel developers who have to stare a lot at assembler listings
252 config UNUSED_SYMBOLS
253 bool "Enable unused/obsolete exported symbols"
256 Unused but exported symbols make the kernel needlessly bigger. For
257 that reason most of these unused exports will soon be removed. This
258 option is provided temporarily to provide a transition period in case
259 some external kernel module needs one of these symbols anyway. If you
260 encounter such a case in your module, consider if you are actually
261 using the right API. (rationale: since nobody in the kernel is using
262 this in a module, there is a pretty good chance it's actually the
263 wrong interface to use). If you really need the symbol, please send a
264 mail to the linux kernel mailing list mentioning the symbol and why
265 you really need it, and what the merge plan to the mainline kernel for
269 bool "Debug Filesystem"
271 debugfs is a virtual file system that kernel developers use to put
272 debugging files into. Enable this option to be able to read and
273 write to these files.
275 For detailed documentation on the debugfs API, see
276 Documentation/filesystems/.
281 bool "Run 'make headers_check' when building vmlinux"
284 This option will extract the user-visible kernel headers whenever
285 building the kernel, and will run basic sanity checks on them to
286 ensure that exported files do not attempt to include files which
287 were not exported, etc.
289 If you're making modifications to header files which are
290 relevant for userspace, say 'Y', and check the headers
291 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
292 your build tree), to make sure they're suitable.
294 config DEBUG_SECTION_MISMATCH
295 bool "Enable full Section mismatch analysis"
297 The section mismatch analysis checks if there are illegal
298 references from one section to another section.
299 During linktime or runtime, some sections are dropped;
300 any use of code/data previously in these sections would
301 most likely result in an oops.
302 In the code, functions and variables are annotated with
303 __init,, etc. (see the full list in include/linux/init.h),
304 which results in the code/data being placed in specific sections.
305 The section mismatch analysis is always performed after a full
306 kernel build, and enabling this option causes the following
307 additional steps to occur:
308 - Add the option -fno-inline-functions-called-once to gcc commands.
309 When inlining a function annotated with __init in a non-init
310 function, we would lose the section information and thus
311 the analysis would not catch the illegal reference.
312 This option tells gcc to inline less (but it does result in
314 - Run the section mismatch analysis for each module/built-in.a file.
315 When we run the section mismatch analysis on vmlinux.o, we
316 lose valuable information about where the mismatch was
318 Running the analysis for each module/built-in.a file
319 tells where the mismatch happens much closer to the
320 source. The drawback is that the same mismatch is
321 reported at least twice.
322 - Enable verbose reporting from modpost in order to help resolve
323 the section mismatches that are reported.
325 config SECTION_MISMATCH_WARN_ONLY
326 bool "Make section mismatch errors non-fatal"
329 If you say N here, the build process will fail if there are any
330 section mismatch, instead of just throwing warnings.
335 # Select this config option from the architecture Kconfig, if it
336 # is preferred to always offer frame pointers as a config
337 # option on the architecture (regardless of KERNEL_DEBUG):
339 config ARCH_WANT_FRAME_POINTERS
343 bool "Compile the kernel with frame pointers"
344 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
345 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
347 If you say Y here the resulting kernel image will be slightly
348 larger and slower, but it gives very useful debugging information
349 in case of kernel bugs. (precise oopses/stacktraces/warnings)
351 config STACK_VALIDATION
352 bool "Compile-time stack metadata validation"
353 depends on HAVE_STACK_VALIDATION
356 Add compile-time checks to validate stack metadata, including frame
357 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
358 that runtime stack traces are more reliable.
360 This is also a prerequisite for generation of ORC unwind data, which
361 is needed for CONFIG_UNWINDER_ORC.
363 For more information, see
364 tools/objtool/Documentation/stack-validation.txt.
366 config DEBUG_FORCE_WEAK_PER_CPU
367 bool "Force weak per-cpu definitions"
368 depends on DEBUG_KERNEL
370 s390 and alpha require percpu variables in modules to be
371 defined weak to work around addressing range issue which
372 puts the following two restrictions on percpu variable
375 1. percpu symbols must be unique whether static or not
376 2. percpu variables can't be defined inside a function
378 To ensure that generic code follows the above rules, this
379 option forces all percpu variables to be defined as weak.
381 endmenu # "Compiler options"
384 bool "Magic SysRq key"
387 If you say Y here, you will have some control over the system even
388 if the system crashes for example during kernel debugging (e.g., you
389 will be able to flush the buffer cache to disk, reboot the system
390 immediately or dump some status information). This is accomplished
391 by pressing various keys while holding SysRq (Alt+PrintScreen). It
392 also works on a serial console (on PC hardware at least), if you
393 send a BREAK and then within 5 seconds a command keypress. The
394 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
395 Don't say Y unless you really know what this hack does.
397 config MAGIC_SYSRQ_DEFAULT_ENABLE
398 hex "Enable magic SysRq key functions by default"
399 depends on MAGIC_SYSRQ
402 Specifies which SysRq key functions are enabled by default.
403 This may be set to 1 or 0 to enable or disable them all, or
404 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
406 config MAGIC_SYSRQ_SERIAL
407 bool "Enable magic SysRq key over serial"
408 depends on MAGIC_SYSRQ
411 Many embedded boards have a disconnected TTL level serial which can
412 generate some garbage that can lead to spurious false sysrq detects.
413 This option allows you to decide whether you want to enable the
417 bool "Kernel debugging"
419 Say Y here if you are developing drivers or trying to debug and
420 identify kernel problems.
422 menu "Memory Debugging"
424 source "mm/Kconfig.debug"
427 bool "Debug object operations"
428 depends on DEBUG_KERNEL
430 If you say Y here, additional code will be inserted into the
431 kernel to track the life time of various objects and validate
432 the operations on those objects.
434 config DEBUG_OBJECTS_SELFTEST
435 bool "Debug objects selftest"
436 depends on DEBUG_OBJECTS
438 This enables the selftest of the object debug code.
440 config DEBUG_OBJECTS_FREE
441 bool "Debug objects in freed memory"
442 depends on DEBUG_OBJECTS
444 This enables checks whether a k/v free operation frees an area
445 which contains an object which has not been deactivated
446 properly. This can make kmalloc/kfree-intensive workloads
449 config DEBUG_OBJECTS_TIMERS
450 bool "Debug timer objects"
451 depends on DEBUG_OBJECTS
453 If you say Y here, additional code will be inserted into the
454 timer routines to track the life time of timer objects and
455 validate the timer operations.
457 config DEBUG_OBJECTS_WORK
458 bool "Debug work objects"
459 depends on DEBUG_OBJECTS
461 If you say Y here, additional code will be inserted into the
462 work queue routines to track the life time of work objects and
463 validate the work operations.
465 config DEBUG_OBJECTS_RCU_HEAD
466 bool "Debug RCU callbacks objects"
467 depends on DEBUG_OBJECTS
469 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
471 config DEBUG_OBJECTS_PERCPU_COUNTER
472 bool "Debug percpu counter objects"
473 depends on DEBUG_OBJECTS
475 If you say Y here, additional code will be inserted into the
476 percpu counter routines to track the life time of percpu counter
477 objects and validate the percpu counter operations.
479 config DEBUG_OBJECTS_ENABLE_DEFAULT
480 int "debug_objects bootup default value (0-1)"
483 depends on DEBUG_OBJECTS
485 Debug objects boot parameter default value
488 bool "Debug slab memory allocations"
489 depends on DEBUG_KERNEL && SLAB
491 Say Y here to have the kernel do limited verification on memory
492 allocation as well as poisoning memory on free to catch use of freed
493 memory. This can make kmalloc/kfree-intensive workloads much slower.
495 config DEBUG_SLAB_LEAK
496 bool "Memory leak debugging"
497 depends on DEBUG_SLAB
500 bool "SLUB debugging on by default"
501 depends on SLUB && SLUB_DEBUG
504 Boot with debugging on by default. SLUB boots by default with
505 the runtime debug capabilities switched off. Enabling this is
506 equivalent to specifying the "slub_debug" parameter on boot.
507 There is no support for more fine grained debug control like
508 possible with slub_debug=xxx. SLUB debugging may be switched
509 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
514 bool "Enable SLUB performance statistics"
515 depends on SLUB && SYSFS
517 SLUB statistics are useful to debug SLUBs allocation behavior in
518 order find ways to optimize the allocator. This should never be
519 enabled for production use since keeping statistics slows down
520 the allocator by a few percentage points. The slabinfo command
521 supports the determination of the most active slabs to figure
522 out which slabs are relevant to a particular load.
523 Try running: slabinfo -DA
525 config HAVE_DEBUG_KMEMLEAK
528 config DEBUG_KMEMLEAK
529 bool "Kernel memory leak detector"
530 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
532 select STACKTRACE if STACKTRACE_SUPPORT
536 Say Y here if you want to enable the memory leak
537 detector. The memory allocation/freeing is traced in a way
538 similar to the Boehm's conservative garbage collector, the
539 difference being that the orphan objects are not freed but
540 only shown in /sys/kernel/debug/kmemleak. Enabling this
541 feature will introduce an overhead to memory
542 allocations. See Documentation/dev-tools/kmemleak.rst for more
545 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
546 of finding leaks due to the slab objects poisoning.
548 In order to access the kmemleak file, debugfs needs to be
549 mounted (usually at /sys/kernel/debug).
551 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
552 int "Maximum kmemleak early log entries"
553 depends on DEBUG_KMEMLEAK
557 Kmemleak must track all the memory allocations to avoid
558 reporting false positives. Since memory may be allocated or
559 freed before kmemleak is initialised, an early log buffer is
560 used to store these actions. If kmemleak reports "early log
561 buffer exceeded", please increase this value.
563 config DEBUG_KMEMLEAK_TEST
564 tristate "Simple test for the kernel memory leak detector"
565 depends on DEBUG_KMEMLEAK && m
567 This option enables a module that explicitly leaks memory.
571 config DEBUG_KMEMLEAK_DEFAULT_OFF
572 bool "Default kmemleak to off"
573 depends on DEBUG_KMEMLEAK
575 Say Y here to disable kmemleak by default. It can then be enabled
576 on the command line via kmemleak=on.
578 config DEBUG_KMEMLEAK_AUTO_SCAN
579 bool "Enable kmemleak auto scan thread on boot up"
581 depends on DEBUG_KMEMLEAK
583 Depending on the cpu, kmemleak scan may be cpu intensive and can
584 stall user tasks at times. This option enables/disables automatic
585 kmemleak scan at boot up.
587 Say N here to disable kmemleak auto scan thread to stop automatic
588 scanning. Disabling this option disables automatic reporting of
593 config DEBUG_STACK_USAGE
594 bool "Stack utilization instrumentation"
595 depends on DEBUG_KERNEL && !IA64
597 Enables the display of the minimum amount of free stack which each
598 task has ever had available in the sysrq-T and sysrq-P debug output.
600 This option will slow down process creation somewhat.
604 depends on DEBUG_KERNEL
606 Enable this to turn on extended checks in the virtual-memory system
607 that may impact performance.
611 config DEBUG_VM_VMACACHE
612 bool "Debug VMA caching"
615 Enable this to turn on VMA caching debug information. Doing so
616 can cause significant overhead, so only enable it in non-production
622 bool "Debug VM red-black trees"
625 Enable VM red-black tree debugging information and extra validations.
629 config DEBUG_VM_PGFLAGS
630 bool "Debug page-flags operations"
633 Enables extra validation on page flags operations.
637 config ARCH_HAS_DEBUG_VIRTUAL
641 bool "Debug VM translations"
642 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
644 Enable some costly sanity checks in virtual to page code. This can
645 catch mistakes with virt_to_page() and friends.
649 config DEBUG_NOMMU_REGIONS
650 bool "Debug the global anon/private NOMMU mapping region tree"
651 depends on DEBUG_KERNEL && !MMU
653 This option causes the global tree of anonymous and private mapping
654 regions to be regularly checked for invalid topology.
656 config DEBUG_MEMORY_INIT
657 bool "Debug memory initialisation" if EXPERT
660 Enable this for additional checks during memory initialisation.
661 The sanity checks verify aspects of the VM such as the memory model
662 and other information provided by the architecture. Verbose
663 information will be printed at KERN_DEBUG loglevel depending
664 on the mminit_loglevel= command-line option.
668 config MEMORY_NOTIFIER_ERROR_INJECT
669 tristate "Memory hotplug notifier error injection module"
670 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
672 This option provides the ability to inject artificial errors to
673 memory hotplug notifier chain callbacks. It is controlled through
674 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
676 If the notifier call chain should be failed with some events
677 notified, write the error code to "actions/<notifier event>/error".
679 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
681 # cd /sys/kernel/debug/notifier-error-inject/memory
682 # echo -12 > actions/MEM_GOING_OFFLINE/error
683 # echo offline > /sys/devices/system/memory/memoryXXX/state
684 bash: echo: write error: Cannot allocate memory
686 To compile this code as a module, choose M here: the module will
687 be called memory-notifier-error-inject.
691 config DEBUG_PER_CPU_MAPS
692 bool "Debug access to per_cpu maps"
693 depends on DEBUG_KERNEL
696 Say Y to verify that the per_cpu map being accessed has
697 been set up. This adds a fair amount of code to kernel memory
698 and decreases performance.
703 bool "Highmem debugging"
704 depends on DEBUG_KERNEL && HIGHMEM
706 This option enables additional error checking for high memory
707 systems. Disable for production systems.
709 config HAVE_DEBUG_STACKOVERFLOW
712 config DEBUG_STACKOVERFLOW
713 bool "Check for stack overflows"
714 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
716 Say Y here if you want to check for overflows of kernel, IRQ
717 and exception stacks (if your architecture uses them). This
718 option will show detailed messages if free stack space drops
719 below a certain limit.
721 These kinds of bugs usually occur when call-chains in the
722 kernel get too deep, especially when interrupts are
725 Use this in cases where you see apparently random memory
726 corruption, especially if it appears in 'struct thread_info'
728 If in doubt, say "N".
730 source "lib/Kconfig.kasan"
732 endmenu # "Memory Debugging"
737 KCOV does not have any arch-specific code, but currently it is enabled
738 only for x86_64. KCOV requires testing on other archs, and most likely
739 disabling of instrumentation for some early boot code.
741 config CC_HAS_SANCOV_TRACE_PC
742 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
745 bool "Code coverage for fuzzing"
746 depends on ARCH_HAS_KCOV
747 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
749 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
751 KCOV exposes kernel code coverage information in a form suitable
752 for coverage-guided fuzzing (randomized testing).
754 If RANDOMIZE_BASE is enabled, PC values will not be stable across
755 different machines and across reboots. If you need stable PC values,
756 disable RANDOMIZE_BASE.
758 For more details, see Documentation/dev-tools/kcov.rst.
760 config KCOV_ENABLE_COMPARISONS
761 bool "Enable comparison operands collection by KCOV"
763 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
765 KCOV also exposes operands of every comparison in the instrumented
766 code along with operand sizes and PCs of the comparison instructions.
767 These operands can be used by fuzzing engines to improve the quality
770 config KCOV_INSTRUMENT_ALL
771 bool "Instrument all code by default"
775 If you are doing generic system call fuzzing (like e.g. syzkaller),
776 then you will want to instrument the whole kernel and you should
777 say y here. If you are doing more targeted fuzzing (like e.g.
778 filesystem fuzzing with AFL) then you will want to enable coverage
779 for more specific subsets of files, and should say n here.
782 bool "Debug shared IRQ handlers"
783 depends on DEBUG_KERNEL
785 Enable this to generate a spurious interrupt as soon as a shared
786 interrupt handler is registered, and just before one is deregistered.
787 Drivers ought to be able to handle interrupts coming in at those
788 points; some don't and need to be caught.
790 menu "Debug Lockups and Hangs"
792 config LOCKUP_DETECTOR
795 config SOFTLOCKUP_DETECTOR
796 bool "Detect Soft Lockups"
797 depends on DEBUG_KERNEL && !S390
798 select LOCKUP_DETECTOR
800 Say Y here to enable the kernel to act as a watchdog to detect
803 Softlockups are bugs that cause the kernel to loop in kernel
804 mode for more than 20 seconds, without giving other tasks a
805 chance to run. The current stack trace is displayed upon
806 detection and the system will stay locked up.
808 config BOOTPARAM_SOFTLOCKUP_PANIC
809 bool "Panic (Reboot) On Soft Lockups"
810 depends on SOFTLOCKUP_DETECTOR
812 Say Y here to enable the kernel to panic on "soft lockups",
813 which are bugs that cause the kernel to loop in kernel
814 mode for more than 20 seconds (configurable using the watchdog_thresh
815 sysctl), without giving other tasks a chance to run.
817 The panic can be used in combination with panic_timeout,
818 to cause the system to reboot automatically after a
819 lockup has been detected. This feature is useful for
820 high-availability systems that have uptime guarantees and
821 where a lockup must be resolved ASAP.
825 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
827 depends on SOFTLOCKUP_DETECTOR
829 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
830 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
832 config HARDLOCKUP_DETECTOR_PERF
834 select SOFTLOCKUP_DETECTOR
837 # Enables a timestamp based low pass filter to compensate for perf based
838 # hard lockup detection which runs too fast due to turbo modes.
840 config HARDLOCKUP_CHECK_TIMESTAMP
844 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
845 # lockup detector rather than the perf based detector.
847 config HARDLOCKUP_DETECTOR
848 bool "Detect Hard Lockups"
849 depends on DEBUG_KERNEL && !S390
850 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
851 select LOCKUP_DETECTOR
852 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
853 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
855 Say Y here to enable the kernel to act as a watchdog to detect
858 Hardlockups are bugs that cause the CPU to loop in kernel mode
859 for more than 10 seconds, without letting other interrupts have a
860 chance to run. The current stack trace is displayed upon detection
861 and the system will stay locked up.
863 config BOOTPARAM_HARDLOCKUP_PANIC
864 bool "Panic (Reboot) On Hard Lockups"
865 depends on HARDLOCKUP_DETECTOR
867 Say Y here to enable the kernel to panic on "hard lockups",
868 which are bugs that cause the kernel to loop in kernel
869 mode with interrupts disabled for more than 10 seconds (configurable
870 using the watchdog_thresh sysctl).
874 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
876 depends on HARDLOCKUP_DETECTOR
878 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
879 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
881 config DETECT_HUNG_TASK
882 bool "Detect Hung Tasks"
883 depends on DEBUG_KERNEL
884 default SOFTLOCKUP_DETECTOR
886 Say Y here to enable the kernel to detect "hung tasks",
887 which are bugs that cause the task to be stuck in
888 uninterruptible "D" state indefinitely.
890 When a hung task is detected, the kernel will print the
891 current stack trace (which you should report), but the
892 task will stay in uninterruptible state. If lockdep is
893 enabled then all held locks will also be reported. This
894 feature has negligible overhead.
896 config DEFAULT_HUNG_TASK_TIMEOUT
897 int "Default timeout for hung task detection (in seconds)"
898 depends on DETECT_HUNG_TASK
901 This option controls the default timeout (in seconds) used
902 to determine when a task has become non-responsive and should
905 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
906 sysctl or by writing a value to
907 /proc/sys/kernel/hung_task_timeout_secs.
909 A timeout of 0 disables the check. The default is two minutes.
910 Keeping the default should be fine in most cases.
912 config BOOTPARAM_HUNG_TASK_PANIC
913 bool "Panic (Reboot) On Hung Tasks"
914 depends on DETECT_HUNG_TASK
916 Say Y here to enable the kernel to panic on "hung tasks",
917 which are bugs that cause the kernel to leave a task stuck
918 in uninterruptible "D" state.
920 The panic can be used in combination with panic_timeout,
921 to cause the system to reboot automatically after a
922 hung task has been detected. This feature is useful for
923 high-availability systems that have uptime guarantees and
924 where a hung tasks must be resolved ASAP.
928 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
930 depends on DETECT_HUNG_TASK
932 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
933 default 1 if BOOTPARAM_HUNG_TASK_PANIC
936 bool "Detect Workqueue Stalls"
937 depends on DEBUG_KERNEL
939 Say Y here to enable stall detection on workqueues. If a
940 worker pool doesn't make forward progress on a pending work
941 item for over a given amount of time, 30s by default, a
942 warning message is printed along with dump of workqueue
943 state. This can be configured through kernel parameter
944 "workqueue.watchdog_thresh" and its sysfs counterpart.
946 endmenu # "Debug lockups and hangs"
951 Say Y here to enable the kernel to panic when it oopses. This
952 has the same effect as setting oops=panic on the kernel command
955 This feature is useful to ensure that the kernel does not do
956 anything erroneous after an oops which could result in data
957 corruption or other issues.
961 config PANIC_ON_OOPS_VALUE
964 default 0 if !PANIC_ON_OOPS
965 default 1 if PANIC_ON_OOPS
971 Set the timeout value (in seconds) until a reboot occurs when the
972 the kernel panics. If n = 0, then we wait forever. A timeout
973 value n > 0 will wait n seconds before rebooting, while a timeout
974 value n < 0 will reboot immediately.
977 bool "Collect scheduler debugging info"
978 depends on DEBUG_KERNEL && PROC_FS
981 If you say Y here, the /proc/sched_debug file will be provided
982 that can help debug the scheduler. The runtime overhead of this
990 bool "Collect scheduler statistics"
991 depends on DEBUG_KERNEL && PROC_FS
994 If you say Y here, additional code will be inserted into the
995 scheduler and related routines to collect statistics about
996 scheduler behavior and provide them in /proc/schedstat. These
997 stats may be useful for both tuning and debugging the scheduler
998 If you aren't debugging the scheduler or trying to tune a specific
999 application, you can say N to avoid the very slight overhead
1002 config SCHED_STACK_END_CHECK
1003 bool "Detect stack corruption on calls to schedule()"
1004 depends on DEBUG_KERNEL
1007 This option checks for a stack overrun on calls to schedule().
1008 If the stack end location is found to be over written always panic as
1009 the content of the corrupted region can no longer be trusted.
1010 This is to ensure no erroneous behaviour occurs which could result in
1011 data corruption or a sporadic crash at a later stage once the region
1012 is examined. The runtime overhead introduced is minimal.
1014 config DEBUG_TIMEKEEPING
1015 bool "Enable extra timekeeping sanity checking"
1017 This option will enable additional timekeeping sanity checks
1018 which may be helpful when diagnosing issues where timekeeping
1019 problems are suspected.
1021 This may include checks in the timekeeping hotpaths, so this
1022 option may have a (very small) performance impact to some
1027 config DEBUG_PREEMPT
1028 bool "Debug preemptible kernel"
1029 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1032 If you say Y here then the kernel will use a debug variant of the
1033 commonly used smp_processor_id() function and will print warnings
1034 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1035 will detect preemption count underflows.
1037 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1039 config LOCK_DEBUGGING_SUPPORT
1041 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1044 config PROVE_LOCKING
1045 bool "Lock debugging: prove locking correctness"
1046 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1048 select DEBUG_SPINLOCK
1049 select DEBUG_MUTEXES
1050 select DEBUG_RT_MUTEXES if RT_MUTEXES
1051 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1052 select DEBUG_WW_MUTEX_SLOWPATH
1053 select DEBUG_LOCK_ALLOC
1054 select TRACE_IRQFLAGS
1057 This feature enables the kernel to prove that all locking
1058 that occurs in the kernel runtime is mathematically
1059 correct: that under no circumstance could an arbitrary (and
1060 not yet triggered) combination of observed locking
1061 sequences (on an arbitrary number of CPUs, running an
1062 arbitrary number of tasks and interrupt contexts) cause a
1065 In short, this feature enables the kernel to report locking
1066 related deadlocks before they actually occur.
1068 The proof does not depend on how hard and complex a
1069 deadlock scenario would be to trigger: how many
1070 participant CPUs, tasks and irq-contexts would be needed
1071 for it to trigger. The proof also does not depend on
1072 timing: if a race and a resulting deadlock is possible
1073 theoretically (no matter how unlikely the race scenario
1074 is), it will be proven so and will immediately be
1075 reported by the kernel (once the event is observed that
1076 makes the deadlock theoretically possible).
1078 If a deadlock is impossible (i.e. the locking rules, as
1079 observed by the kernel, are mathematically correct), the
1080 kernel reports nothing.
1082 NOTE: this feature can also be enabled for rwlocks, mutexes
1083 and rwsems - in which case all dependencies between these
1084 different locking variants are observed and mapped too, and
1085 the proof of observed correctness is also maintained for an
1086 arbitrary combination of these separate locking variants.
1088 For more details, see Documentation/locking/lockdep-design.txt.
1091 bool "Lock usage statistics"
1092 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1094 select DEBUG_SPINLOCK
1095 select DEBUG_MUTEXES
1096 select DEBUG_RT_MUTEXES if RT_MUTEXES
1097 select DEBUG_LOCK_ALLOC
1100 This feature enables tracking lock contention points
1102 For more details, see Documentation/locking/lockstat.txt
1104 This also enables lock events required by "perf lock",
1106 If you want to use "perf lock", you also need to turn on
1107 CONFIG_EVENT_TRACING.
1109 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1110 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1112 config DEBUG_RT_MUTEXES
1113 bool "RT Mutex debugging, deadlock detection"
1114 depends on DEBUG_KERNEL && RT_MUTEXES
1116 This allows rt mutex semantics violations and rt mutex related
1117 deadlocks (lockups) to be detected and reported automatically.
1119 config DEBUG_SPINLOCK
1120 bool "Spinlock and rw-lock debugging: basic checks"
1121 depends on DEBUG_KERNEL
1122 select UNINLINE_SPIN_UNLOCK
1124 Say Y here and build SMP to catch missing spinlock initialization
1125 and certain other kinds of spinlock errors commonly made. This is
1126 best used in conjunction with the NMI watchdog so that spinlock
1127 deadlocks are also debuggable.
1129 config DEBUG_MUTEXES
1130 bool "Mutex debugging: basic checks"
1131 depends on DEBUG_KERNEL
1133 This feature allows mutex semantics violations to be detected and
1136 config DEBUG_WW_MUTEX_SLOWPATH
1137 bool "Wait/wound mutex debugging: Slowpath testing"
1138 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1139 select DEBUG_LOCK_ALLOC
1140 select DEBUG_SPINLOCK
1141 select DEBUG_MUTEXES
1143 This feature enables slowpath testing for w/w mutex users by
1144 injecting additional -EDEADLK wound/backoff cases. Together with
1145 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1146 will test all possible w/w mutex interface abuse with the
1147 exception of simply not acquiring all the required locks.
1148 Note that this feature can introduce significant overhead, so
1149 it really should not be enabled in a production or distro kernel,
1150 even a debug kernel. If you are a driver writer, enable it. If
1151 you are a distro, do not.
1154 bool "RW Semaphore debugging: basic checks"
1155 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1157 This debugging feature allows mismatched rw semaphore locks and unlocks
1158 to be detected and reported.
1160 config DEBUG_LOCK_ALLOC
1161 bool "Lock debugging: detect incorrect freeing of live locks"
1162 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1163 select DEBUG_SPINLOCK
1164 select DEBUG_MUTEXES
1165 select DEBUG_RT_MUTEXES if RT_MUTEXES
1168 This feature will check whether any held lock (spinlock, rwlock,
1169 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1170 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1171 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1172 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1173 held during task exit.
1177 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1179 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1183 config LOCKDEP_SMALL
1186 config DEBUG_LOCKDEP
1187 bool "Lock dependency engine debugging"
1188 depends on DEBUG_KERNEL && LOCKDEP
1190 If you say Y here, the lock dependency engine will do
1191 additional runtime checks to debug itself, at the price
1192 of more runtime overhead.
1194 config DEBUG_ATOMIC_SLEEP
1195 bool "Sleep inside atomic section checking"
1196 select PREEMPT_COUNT
1197 depends on DEBUG_KERNEL
1198 depends on !ARCH_NO_PREEMPT
1200 If you say Y here, various routines which may sleep will become very
1201 noisy if they are called inside atomic sections: when a spinlock is
1202 held, inside an rcu read side critical section, inside preempt disabled
1203 sections, inside an interrupt, etc...
1205 config DEBUG_LOCKING_API_SELFTESTS
1206 bool "Locking API boot-time self-tests"
1207 depends on DEBUG_KERNEL
1209 Say Y here if you want the kernel to run a short self-test during
1210 bootup. The self-test checks whether common types of locking bugs
1211 are detected by debugging mechanisms or not. (if you disable
1212 lock debugging then those bugs wont be detected of course.)
1213 The following locking APIs are covered: spinlocks, rwlocks,
1216 config LOCK_TORTURE_TEST
1217 tristate "torture tests for locking"
1218 depends on DEBUG_KERNEL
1221 This option provides a kernel module that runs torture tests
1222 on kernel locking primitives. The kernel module may be built
1223 after the fact on the running kernel to be tested, if desired.
1225 Say Y here if you want kernel locking-primitive torture tests
1226 to be built into the kernel.
1227 Say M if you want these torture tests to build as a module.
1228 Say N if you are unsure.
1230 config WW_MUTEX_SELFTEST
1231 tristate "Wait/wound mutex selftests"
1233 This option provides a kernel module that runs tests on the
1234 on the struct ww_mutex locking API.
1236 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1237 with this test harness.
1239 Say M if you want these self tests to build as a module.
1240 Say N if you are unsure.
1242 endmenu # lock debugging
1244 config TRACE_IRQFLAGS
1247 Enables hooks to interrupt enabling and disabling for
1248 either tracing or lock debugging.
1251 bool "Stack backtrace support"
1252 depends on STACKTRACE_SUPPORT
1254 This option causes the kernel to create a /proc/pid/stack for
1255 every process, showing its current stack trace.
1256 It is also used by various kernel debugging features that require
1257 stack trace generation.
1259 config WARN_ALL_UNSEEDED_RANDOM
1260 bool "Warn for all uses of unseeded randomness"
1263 Some parts of the kernel contain bugs relating to their use of
1264 cryptographically secure random numbers before it's actually possible
1265 to generate those numbers securely. This setting ensures that these
1266 flaws don't go unnoticed, by enabling a message, should this ever
1267 occur. This will allow people with obscure setups to know when things
1268 are going wrong, so that they might contact developers about fixing
1271 Unfortunately, on some models of some architectures getting
1272 a fully seeded CRNG is extremely difficult, and so this can
1273 result in dmesg getting spammed for a surprisingly long
1274 time. This is really bad from a security perspective, and
1275 so architecture maintainers really need to do what they can
1276 to get the CRNG seeded sooner after the system is booted.
1277 However, since users cannot do anything actionable to
1278 address this, by default the kernel will issue only a single
1279 warning for the first use of unseeded randomness.
1281 Say Y here if you want to receive warnings for all uses of
1282 unseeded randomness. This will be of use primarily for
1283 those developers interested in improving the security of
1284 Linux kernels running on their architecture (or
1287 config DEBUG_KOBJECT
1288 bool "kobject debugging"
1289 depends on DEBUG_KERNEL
1291 If you say Y here, some extra kobject debugging messages will be sent
1294 config DEBUG_KOBJECT_RELEASE
1295 bool "kobject release debugging"
1296 depends on DEBUG_OBJECTS_TIMERS
1298 kobjects are reference counted objects. This means that their
1299 last reference count put is not predictable, and the kobject can
1300 live on past the point at which a driver decides to drop it's
1301 initial reference to the kobject gained on allocation. An
1302 example of this would be a struct device which has just been
1305 However, some buggy drivers assume that after such an operation,
1306 the memory backing the kobject can be immediately freed. This
1307 goes completely against the principles of a refcounted object.
1309 If you say Y here, the kernel will delay the release of kobjects
1310 on the last reference count to improve the visibility of this
1311 kind of kobject release bug.
1313 config HAVE_DEBUG_BUGVERBOSE
1316 config DEBUG_BUGVERBOSE
1317 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1318 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1321 Say Y here to make BUG() panics output the file name and line number
1322 of the BUG call as well as the EIP and oops trace. This aids
1323 debugging but costs about 70-100K of memory.
1326 bool "Debug linked list manipulation"
1327 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1329 Enable this to turn on extended checks in the linked-list
1334 config DEBUG_PI_LIST
1335 bool "Debug priority linked list manipulation"
1336 depends on DEBUG_KERNEL
1338 Enable this to turn on extended checks in the priority-ordered
1339 linked-list (plist) walking routines. This checks the entire
1340 list multiple times during each manipulation.
1345 bool "Debug SG table operations"
1346 depends on DEBUG_KERNEL
1348 Enable this to turn on checks on scatter-gather tables. This can
1349 help find problems with drivers that do not properly initialize
1354 config DEBUG_NOTIFIERS
1355 bool "Debug notifier call chains"
1356 depends on DEBUG_KERNEL
1358 Enable this to turn on sanity checking for notifier call chains.
1359 This is most useful for kernel developers to make sure that
1360 modules properly unregister themselves from notifier chains.
1361 This is a relatively cheap check but if you care about maximum
1364 config DEBUG_CREDENTIALS
1365 bool "Debug credential management"
1366 depends on DEBUG_KERNEL
1368 Enable this to turn on some debug checking for credential
1369 management. The additional code keeps track of the number of
1370 pointers from task_structs to any given cred struct, and checks to
1371 see that this number never exceeds the usage count of the cred
1374 Furthermore, if SELinux is enabled, this also checks that the
1375 security pointer in the cred struct is never seen to be invalid.
1379 source "kernel/rcu/Kconfig.debug"
1381 config DEBUG_WQ_FORCE_RR_CPU
1382 bool "Force round-robin CPU selection for unbound work items"
1383 depends on DEBUG_KERNEL
1386 Workqueue used to implicitly guarantee that work items queued
1387 without explicit CPU specified are put on the local CPU. This
1388 guarantee is no longer true and while local CPU is still
1389 preferred work items may be put on foreign CPUs. Kernel
1390 parameter "workqueue.debug_force_rr_cpu" is added to force
1391 round-robin CPU selection to flush out usages which depend on the
1392 now broken guarantee. This config option enables the debug
1393 feature by default. When enabled, memory and cache locality will
1396 config DEBUG_BLOCK_EXT_DEVT
1397 bool "Force extended block device numbers and spread them"
1398 depends on DEBUG_KERNEL
1402 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1403 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1404 YOU ARE DOING. Distros, please enable this and fix whatever
1407 Conventionally, block device numbers are allocated from
1408 predetermined contiguous area. However, extended block area
1409 may introduce non-contiguous block device numbers. This
1410 option forces most block device numbers to be allocated from
1411 the extended space and spreads them to discover kernel or
1412 userland code paths which assume predetermined contiguous
1413 device number allocation.
1415 Note that turning on this debug option shuffles all the
1416 device numbers for all IDE and SCSI devices including libata
1417 ones, so root partition specified using device number
1418 directly (via rdev or root=MAJ:MIN) won't work anymore.
1419 Textual device names (root=/dev/sdXn) will continue to work.
1421 Say N if you are unsure.
1423 config CPU_HOTPLUG_STATE_CONTROL
1424 bool "Enable CPU hotplug state control"
1425 depends on DEBUG_KERNEL
1426 depends on HOTPLUG_CPU
1429 Allows to write steps between "offline" and "online" to the CPUs
1430 sysfs target file so states can be stepped granular. This is a debug
1431 option for now as the hotplug machinery cannot be stopped and
1432 restarted at arbitrary points yet.
1434 Say N if your are unsure.
1436 config NOTIFIER_ERROR_INJECTION
1437 tristate "Notifier error injection"
1438 depends on DEBUG_KERNEL
1441 This option provides the ability to inject artificial errors to
1442 specified notifier chain callbacks. It is useful to test the error
1443 handling of notifier call chain failures.
1447 config PM_NOTIFIER_ERROR_INJECT
1448 tristate "PM notifier error injection module"
1449 depends on PM && NOTIFIER_ERROR_INJECTION
1450 default m if PM_DEBUG
1452 This option provides the ability to inject artificial errors to
1453 PM notifier chain callbacks. It is controlled through debugfs
1454 interface /sys/kernel/debug/notifier-error-inject/pm
1456 If the notifier call chain should be failed with some events
1457 notified, write the error code to "actions/<notifier event>/error".
1459 Example: Inject PM suspend error (-12 = -ENOMEM)
1461 # cd /sys/kernel/debug/notifier-error-inject/pm/
1462 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1463 # echo mem > /sys/power/state
1464 bash: echo: write error: Cannot allocate memory
1466 To compile this code as a module, choose M here: the module will
1467 be called pm-notifier-error-inject.
1471 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1472 tristate "OF reconfig notifier error injection module"
1473 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1475 This option provides the ability to inject artificial errors to
1476 OF reconfig notifier chain callbacks. It is controlled
1477 through debugfs interface under
1478 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1480 If the notifier call chain should be failed with some events
1481 notified, write the error code to "actions/<notifier event>/error".
1483 To compile this code as a module, choose M here: the module will
1484 be called of-reconfig-notifier-error-inject.
1488 config NETDEV_NOTIFIER_ERROR_INJECT
1489 tristate "Netdev notifier error injection module"
1490 depends on NET && NOTIFIER_ERROR_INJECTION
1492 This option provides the ability to inject artificial errors to
1493 netdevice notifier chain callbacks. It is controlled through debugfs
1494 interface /sys/kernel/debug/notifier-error-inject/netdev
1496 If the notifier call chain should be failed with some events
1497 notified, write the error code to "actions/<notifier event>/error".
1499 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1501 # cd /sys/kernel/debug/notifier-error-inject/netdev
1502 # echo -22 > actions/NETDEV_CHANGEMTU/error
1503 # ip link set eth0 mtu 1024
1504 RTNETLINK answers: Invalid argument
1506 To compile this code as a module, choose M here: the module will
1507 be called netdev-notifier-error-inject.
1511 config FUNCTION_ERROR_INJECTION
1513 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1515 config FAULT_INJECTION
1516 bool "Fault-injection framework"
1517 depends on DEBUG_KERNEL
1519 Provide fault-injection framework.
1520 For more details, see Documentation/fault-injection/.
1523 bool "Fault-injection capability for kmalloc"
1524 depends on FAULT_INJECTION
1525 depends on SLAB || SLUB
1527 Provide fault-injection capability for kmalloc.
1529 config FAIL_PAGE_ALLOC
1530 bool "Fault-injection capabilitiy for alloc_pages()"
1531 depends on FAULT_INJECTION
1533 Provide fault-injection capability for alloc_pages().
1535 config FAIL_MAKE_REQUEST
1536 bool "Fault-injection capability for disk IO"
1537 depends on FAULT_INJECTION && BLOCK
1539 Provide fault-injection capability for disk IO.
1541 config FAIL_IO_TIMEOUT
1542 bool "Fault-injection capability for faking disk interrupts"
1543 depends on FAULT_INJECTION && BLOCK
1545 Provide fault-injection capability on end IO handling. This
1546 will make the block layer "forget" an interrupt as configured,
1547 thus exercising the error handling.
1549 Only works with drivers that use the generic timeout handling,
1550 for others it wont do anything.
1553 bool "Fault-injection capability for futexes"
1555 depends on FAULT_INJECTION && FUTEX
1557 Provide fault-injection capability for futexes.
1559 config FAULT_INJECTION_DEBUG_FS
1560 bool "Debugfs entries for fault-injection capabilities"
1561 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1563 Enable configuration of fault-injection capabilities via debugfs.
1565 config FAIL_FUNCTION
1566 bool "Fault-injection capability for functions"
1567 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1569 Provide function-based fault-injection capability.
1570 This will allow you to override a specific function with a return
1571 with given return value. As a result, function caller will see
1572 an error value and have to handle it. This is useful to test the
1573 error handling in various subsystems.
1575 config FAIL_MMC_REQUEST
1576 bool "Fault-injection capability for MMC IO"
1577 depends on FAULT_INJECTION_DEBUG_FS && MMC
1579 Provide fault-injection capability for MMC IO.
1580 This will make the mmc core return data errors. This is
1581 useful to test the error handling in the mmc block device
1582 and to test how the mmc host driver handles retries from
1585 config FAULT_INJECTION_STACKTRACE_FILTER
1586 bool "stacktrace filter for fault-injection capabilities"
1587 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1590 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1592 Provide stacktrace filter for fault-injection capabilities
1595 bool "Latency measuring infrastructure"
1596 depends on DEBUG_KERNEL
1597 depends on STACKTRACE_SUPPORT
1599 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1606 Enable this option if you want to use the LatencyTOP tool
1607 to find out which userspace is blocking on what kernel operations.
1609 source "kernel/trace/Kconfig"
1611 config PROVIDE_OHCI1394_DMA_INIT
1612 bool "Remote debugging over FireWire early on boot"
1613 depends on PCI && X86
1615 If you want to debug problems which hang or crash the kernel early
1616 on boot and the crashing machine has a FireWire port, you can use
1617 this feature to remotely access the memory of the crashed machine
1618 over FireWire. This employs remote DMA as part of the OHCI1394
1619 specification which is now the standard for FireWire controllers.
1621 With remote DMA, you can monitor the printk buffer remotely using
1622 firescope and access all memory below 4GB using fireproxy from gdb.
1623 Even controlling a kernel debugger is possible using remote DMA.
1627 If ohci1394_dma=early is used as boot parameter, it will initialize
1628 all OHCI1394 controllers which are found in the PCI config space.
1630 As all changes to the FireWire bus such as enabling and disabling
1631 devices cause a bus reset and thereby disable remote DMA for all
1632 devices, be sure to have the cable plugged and FireWire enabled on
1633 the debugging host before booting the debug target for debugging.
1635 This code (~1k) is freed after boot. By then, the firewire stack
1636 in charge of the OHCI-1394 controllers should be used instead.
1638 See Documentation/debugging-via-ohci1394.txt for more information.
1640 config DMA_API_DEBUG
1641 bool "Enable debugging of DMA-API usage"
1642 select NEED_DMA_MAP_STATE
1644 Enable this option to debug the use of the DMA API by device drivers.
1645 With this option you will be able to detect common bugs in device
1646 drivers like double-freeing of DMA mappings or freeing mappings that
1647 were never allocated.
1649 This also attempts to catch cases where a page owned by DMA is
1650 accessed by the cpu in a way that could cause data corruption. For
1651 example, this enables cow_user_page() to check that the source page is
1654 This option causes a performance degradation. Use only if you want to
1655 debug device drivers and dma interactions.
1659 config DMA_API_DEBUG_SG
1660 bool "Debug DMA scatter-gather usage"
1662 depends on DMA_API_DEBUG
1664 Perform extra checking that callers of dma_map_sg() have respected the
1665 appropriate segment length/boundary limits for the given device when
1666 preparing DMA scatterlists.
1668 This is particularly likely to have been overlooked in cases where the
1669 dma_map_sg() API is used for general bulk mapping of pages rather than
1670 preparing literal scatter-gather descriptors, where there is a risk of
1671 unexpected behaviour from DMA API implementations if the scatterlist
1672 is technically out-of-spec.
1676 menuconfig RUNTIME_TESTING_MENU
1677 bool "Runtime Testing"
1680 if RUNTIME_TESTING_MENU
1683 tristate "Linux Kernel Dump Test Tool Module"
1686 This module enables testing of the different dumping mechanisms by
1687 inducing system failures at predefined crash points.
1688 If you don't need it: say N
1689 Choose M here to compile this code as a module. The module will be
1692 Documentation on how to use the module can be found in
1693 Documentation/fault-injection/provoke-crashes.txt
1695 config TEST_LIST_SORT
1696 tristate "Linked list sorting test"
1697 depends on DEBUG_KERNEL || m
1699 Enable this to turn on 'list_sort()' function test. This test is
1700 executed only once during system boot (so affects only boot time),
1701 or at module load time.
1706 tristate "Array-based sort test"
1707 depends on DEBUG_KERNEL || m
1709 This option enables the self-test function of 'sort()' at boot,
1710 or at module load time.
1714 config KPROBES_SANITY_TEST
1715 bool "Kprobes sanity tests"
1716 depends on DEBUG_KERNEL
1719 This option provides for testing basic kprobes functionality on
1720 boot. Samples of kprobe and kretprobe are inserted and
1721 verified for functionality.
1723 Say N if you are unsure.
1725 config BACKTRACE_SELF_TEST
1726 tristate "Self test for the backtrace code"
1727 depends on DEBUG_KERNEL
1729 This option provides a kernel module that can be used to test
1730 the kernel stack backtrace code. This option is not useful
1731 for distributions or general kernels, but only for kernel
1732 developers working on architecture code.
1734 Note that if you want to also test saved backtraces, you will
1735 have to enable STACKTRACE as well.
1737 Say N if you are unsure.
1740 tristate "Red-Black tree test"
1741 depends on DEBUG_KERNEL
1743 A benchmark measuring the performance of the rbtree library.
1744 Also includes rbtree invariant checks.
1746 config INTERVAL_TREE_TEST
1747 tristate "Interval tree test"
1748 depends on DEBUG_KERNEL
1749 select INTERVAL_TREE
1751 A benchmark measuring the performance of the interval tree library
1754 tristate "Per cpu operations test"
1755 depends on m && DEBUG_KERNEL
1757 Enable this option to build test module which validates per-cpu
1762 config ATOMIC64_SELFTEST
1763 tristate "Perform an atomic64_t self-test"
1765 Enable this option to test the atomic64_t functions at boot or
1766 at module load time.
1770 config ASYNC_RAID6_TEST
1771 tristate "Self test for hardware accelerated raid6 recovery"
1772 depends on ASYNC_RAID6_RECOV
1775 This is a one-shot self test that permutes through the
1776 recovery of all the possible two disk failure scenarios for a
1777 N-disk array. Recovery is performed with the asynchronous
1778 raid6 recovery routines, and will optionally use an offload
1779 engine if one is available.
1784 tristate "Test functions located in the hexdump module at runtime"
1786 config TEST_STRING_HELPERS
1787 tristate "Test functions located in the string_helpers module at runtime"
1790 tristate "Test kstrto*() family of functions at runtime"
1793 tristate "Test printf() family of functions at runtime"
1796 tristate "Test bitmap_*() family of functions at runtime"
1798 Enable this option to test the bitmap functions at boot.
1802 config TEST_BITFIELD
1803 tristate "Test bitfield functions at runtime"
1805 Enable this option to test the bitfield functions at boot.
1810 tristate "Test functions located in the uuid module at runtime"
1813 tristate "Test the XArray code at runtime"
1815 config TEST_OVERFLOW
1816 tristate "Test check_*_overflow() functions at runtime"
1818 config TEST_RHASHTABLE
1819 tristate "Perform selftest on resizable hash table"
1821 Enable this option to test the rhashtable functions at boot.
1826 tristate "Perform selftest on hash functions"
1828 Enable this option to test the kernel's integer (<linux/hash.h>),
1829 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1830 hash functions on boot (or module load).
1832 This is intended to help people writing architecture-specific
1833 optimized versions. If unsure, say N.
1836 tristate "Perform selftest on IDA functions"
1839 tristate "Perform selftest on priority array manager"
1842 Enable this option to test priority array manager on boot
1848 tristate "Test module loading with 'hello world' module"
1851 This builds the "test_module" module that emits "Hello, world"
1852 on printk when loaded. It is designed to be used for basic
1853 evaluation of the module loading subsystem (for example when
1854 validating module verification). It lacks any extra dependencies,
1855 and will not normally be loaded by the system unless explicitly
1861 tristate "Test module for stress/performance analysis of vmalloc allocator"
1866 This builds the "test_vmalloc" module that should be used for
1867 stress and performance analysis. So, any new change for vmalloc
1868 subsystem can be evaluated from performance and stability point
1873 config TEST_USER_COPY
1874 tristate "Test user/kernel boundary protections"
1877 This builds the "test_user_copy" module that runs sanity checks
1878 on the copy_to/from_user infrastructure, making sure basic
1879 user/kernel boundary testing is working. If it fails to load,
1880 a regression has been detected in the user/kernel memory boundary
1886 tristate "Test BPF filter functionality"
1889 This builds the "test_bpf" module that runs various test vectors
1890 against the BPF interpreter or BPF JIT compiler depending on the
1891 current setting. This is in particular useful for BPF JIT compiler
1892 development, but also to run regression tests against changes in
1893 the interpreter code. It also enables test stubs for eBPF maps and
1894 verifier used by user space verifier testsuite.
1898 config FIND_BIT_BENCHMARK
1899 tristate "Test find_bit functions"
1901 This builds the "test_find_bit" module that measure find_*_bit()
1902 functions performance.
1906 config TEST_FIRMWARE
1907 tristate "Test firmware loading via userspace interface"
1908 depends on FW_LOADER
1910 This builds the "test_firmware" module that creates a userspace
1911 interface for testing firmware loading. This can be used to
1912 control the triggering of firmware loading without needing an
1913 actual firmware-using device. The contents can be rechecked by
1919 tristate "sysctl test driver"
1920 depends on PROC_SYSCTL
1922 This builds the "test_sysctl" module. This driver enables to test the
1923 proc sysctl interfaces available to drivers safely without affecting
1924 production knobs which might alter system functionality.
1929 tristate "udelay test driver"
1931 This builds the "udelay_test" module that helps to make sure
1932 that udelay() is working properly.
1936 config TEST_STATIC_KEYS
1937 tristate "Test static keys"
1940 Test the static key interfaces.
1945 tristate "kmod stress tester"
1947 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1948 depends on NETDEVICES && NET_CORE && INET # for TUN
1954 Test the kernel's module loading mechanism: kmod. kmod implements
1955 support to load modules using the Linux kernel's usermode helper.
1956 This test provides a series of tests against kmod.
1958 Although technically you can either build test_kmod as a module or
1959 into the kernel we disallow building it into the kernel since
1960 it stress tests request_module() and this will very likely cause
1961 some issues by taking over precious threads available from other
1962 module load requests, ultimately this could be fatal.
1966 tools/testing/selftests/kmod/kmod.sh --help
1970 config TEST_DEBUG_VIRTUAL
1971 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1972 depends on DEBUG_VIRTUAL
1974 Test the kernel's ability to detect incorrect calls to
1975 virt_to_phys() done against the non-linear part of the
1976 kernel's virtual address map.
1980 config TEST_MEMCAT_P
1981 tristate "Test memcat_p() helper function"
1983 Test the memcat_p() helper for correctly merging two
1984 pointer arrays together.
1989 tristate "Perform selftest on object aggreration manager"
1993 Enable this option to test object aggregation manager on boot
1998 endif # RUNTIME_TESTING_MENU
2003 This option adds a kernel parameter 'memtest', which allows memtest
2005 memtest=0, mean disabled; -- default
2006 memtest=1, mean do 1 test pattern;
2008 memtest=17, mean do 17 test patterns.
2009 If you are unsure how to answer this question, answer N.
2011 config BUG_ON_DATA_CORRUPTION
2012 bool "Trigger a BUG when data corruption is detected"
2015 Select this option if the kernel should BUG when it encounters
2016 data corruption in kernel memory structures when they get checked
2021 source "samples/Kconfig"
2023 source "lib/Kconfig.kgdb"
2025 source "lib/Kconfig.ubsan"
2027 config ARCH_HAS_DEVMEM_IS_ALLOWED
2030 config STRICT_DEVMEM
2031 bool "Filter access to /dev/mem"
2032 depends on MMU && DEVMEM
2033 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2034 default y if PPC || X86 || ARM64
2036 If this option is disabled, you allow userspace (root) access to all
2037 of memory, including kernel and userspace memory. Accidental
2038 access to this is obviously disastrous, but specific access can
2039 be used by people debugging the kernel. Note that with PAT support
2040 enabled, even in this case there are restrictions on /dev/mem
2041 use due to the cache aliasing requirements.
2043 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2044 file only allows userspace access to PCI space and the BIOS code and
2045 data regions. This is sufficient for dosemu and X and all common
2050 config IO_STRICT_DEVMEM
2051 bool "Filter I/O access to /dev/mem"
2052 depends on STRICT_DEVMEM
2054 If this option is disabled, you allow userspace (root) access to all
2055 io-memory regardless of whether a driver is actively using that
2056 range. Accidental access to this is obviously disastrous, but
2057 specific access can be used by people debugging kernel drivers.
2059 If this option is switched on, the /dev/mem file only allows
2060 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2061 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2062 if the driver using a given range cannot be disabled.
2066 source "arch/$(SRCARCH)/Kconfig.debug"
2068 endmenu # Kernel hacking
projects / linux.git / blob